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Rheological behavior in melt of aliphatic hyperbranched polyesters (AHBP), synthesized using pseudo-one-step and one-step procedure, was investigated in this work. Three commercially available AHBP were also examined. Because of the presence of relatively strong hydrogen bonds between numerous end hydroxyl groups, AHBP of lower generation number, as well as the sample of tenth pseudo generation, show non-Newtonian behavior in the entire investigated frequency and temperature region. However, for other examined AHBP, the slope of the frequency dependence of complex viscosity (g* ¼ f(x)) becomes smaller with the temperature increase. Therefore, samples of fourth, fifth, and sixth pseudo generations show Newtonian behavior at temperatures higher than 70 C. Value of glass transition temperature, melt flow activation energy, fractional free volume, and thermal expansion coefficient were determined for the investigated AHBP. The influence of the type of end groups on rheological properties of AHBP was also examined.

The rheological investigation of concentrated solutions of aliphatic hyperbranched polyesters (AHBP) in N‐methyl‐2‐pyrrolidinon (NMP) is presented. Two series of hydroxy‐functional AHBP were synthesized using pseudo‐one‐step and one‐step procedure. Three commercial (Boltorn®) AHBP were also investigated. In the examined temperature region (10–50 °C), AHBP solutions (c ≤ 45 wt.‐%) exhibited Newtonian behavior. The same was observed for 50 and 55 wt.‐% solutions at T ≥ 40 °C. However, at T < 50 °C, solutions of AHBP of higher concentrations (50 and 55 wt.‐%) showed shear thinning behavior. Values of the flow activation energies were calculated for all examined AHBP. The influence of the procedure for the synthesis, concentration and temperature on rheological behavior of AHBP solutions in NMP is discussed.magnified image

Kappa-, iota-, and lambda-carrageenan (food grade) were analyzed by static light scattering (MALS in batch mode) in 0.1M NaNO 3 at 25 and 60 C, earlier heated up to 90 C or not. At 25 C, there was a strong tendency for a concentration-dependent aggregation in the order lambda < kappa < iota. At 60 C, all samples were molecularly dispersed. The strongly temperature-dependent refractive index increments (equilibrium dialysis) differ. Data interpretation in terms of the wormlike chain model using the Skolnik-Odijk-Fixman approach led to an intrinsic persistence length around 3 to 4 nm and expansion factors as high as 1.5 and above in a thermodynamically good solvent for all three types. and a nearly identical molar mass dependence of the radius of gyration. HPSEC at 25 C on kappa-carrageenan confirmed formation of soluble aggregates. Special emphasis was put on analytical and methodological aspects. The reliability of the experimental data was demonstrated by analogous measurements on dextran calibration standards.